Abstract. We present a selection of methodologies for using the palaeo-climate model
component of the Coupled Model Intercomparison Project (Phase 5) (CMIP5) to
attempt to constrain future climate projections using the same models.
The constraints arise from measures of skill in hindcasting palaeo-climate
changes from the present over three periods: the Last Glacial Maximum (LGM)
(21 000 yr before present, ka), the mid-Holocene (MH) (6 ka) and the
Last Millennium (LM) (850–1850 CE). The skill measures may be used to
validate robust patterns of climate change across scenarios or to
distinguish between models that have differing outcomes in future scenarios.
We find that the multi-model ensemble of palaeo-simulations is adequate for
addressing at least some of these issues. For example, selected benchmarks
for the LGM and MH are correlated to the rank of future projections of
precipitation/temperature or sea ice extent to indicate that models that
produce the best agreement with palaeo-climate information give demonstrably
different future results than the rest of the models. We also explore cases
where comparisons are strongly dependent on uncertain forcing time series or
show important non-stationarity, making direct inferences for the future
problematic. Overall, we demonstrate that there is a strong potential for
the palaeo-climate simulations to help inform the future projections and urge
all the modelling groups to complete this subset of the CMIP5 runs.